Chapter 37: Surgery for Functional Mitral Regurgitation

INTRODUCTION

Functional mitral regurgitation (FMR) is a complication of ischemic or dilated cardiomyopathy, occurring secondary to left ventricular (LV) geometrical distortion from tenting, inferobasilar migration, apical displacement, annular dilation and posterior leaflet restriction, and/or regional LV wall dysfunction. MR leads to a vicious cycle of LV volume overload, increased geometric distortion and progressive MR. FMR complicating congestive heart failure predicts a poor survival. Mitral surgery, to treat FMR has been undertaken with an acceptably low operative mortality. However, the exact MR surgery (repair or replacement) for which patient and what benefit, remains controversial.

Congestive heart failure is one of the world’s leading causes of morbidity and mortality. As our population ages, the number of patients suffering from end-stage heart failure will continue to rise. In the United States alone, there are nearly 7 million patients suffering from heart failure. In 2012, heart failure “therapy” cost the United States over $50 billion. This total includes health care services, medications, and lost productivity. Yet of the 700,000 new congestive heart failure (CHF) patients diagnosed each year, less than 3000 are offered transplantation due to limitations of age, comorbid conditions and donor availability. Even fewer are presently served with a mechanical assist device. One of the most common (up to 50% of patients) and serious problems in cardiomyopathy is the development of functional or secondary mitral regurgitation. Functional mitral regurgitation (FMR), nonorganic mitral valve (MV) disease, may eventually affect almost all heart failure patients as a preterminal or terminal event.¹ FMR is not caused by intrinsic disease of the valve, but by left ventricular (LV) remodeling, dilation, and dysfunction leading to geometric reconfiguration of the mitroventricular apparatus, including papillary muscle displacement and annular dilation. MV leaflets become tethered, with failure of anterior-posterior leaflet coaptation, resulting in symmetric or asymmetric regurgitation.^2,3 The progressive dilatation of the left ventricle initially gives rise to FMR that begets further ventricular dilatation and more FMR. FMR is associated with poor quality of life and a reduction in long-term survival. Mitral surgery, while not addressing the underlying ventricular pathology, hopefully could interrupt this cycle of ventricular deterioration through the restoration of mitral competency.

BACKGROUND

It has been well documented that even small amounts of FMR are harmful in CHF patients. Grigioni et al⁴ showed that when FMR regurgitant volume was >30 ml the 5-year survival was <35% compared to 44% for a regurgitant volumes of 1 to 29 ml and 61% for CHF patients with no MR. Bursi⁵ also examined the role of FMR and its impact in CHF. CHF patients (469) were followed for mortality according to severity of their FMR. Their 5-year survival was 83% in patients with no/1+ FMR, 64% in 2+, 58% in 3+, and 46% in 4 + (p < .0001). The association between FMR and Major Adverse Cardiac and Cerebrovascular Events (MACCE) was strong and independent in ...